I’m buying some PCBs for my arcade cabinet on eBay.  I’m currently focusing on “parts”, “untested” and “junk” boards in hopes of honing my repair skills.

Buying games as “parts” is risky, and usually a bit of work.  It’s a chance for you to get something under market value.  You might wind up with something that works perfectly because the seller couldn’t actually test it.  It might have a fault that you may or mat not be able to fix, or you might get a box full of bricks.  I took a chance and found a reliable seller.  This is the first of many game boards I’ll receive from him.

So, this is Last Mission.  Immediate problems:  RAM check “110″ result is  ‘ERR” during start-up test.  Despite this, the game usually boots right up into attract mode, but occasionally, the board will loop through the self-check a few times (indicating that something is wrong).  There doesn’t appear to be any graphical glitches, and all the inputs seem to work.  Sound is good until some combination of sound effects overloads the output, which sends some static out to the speakers.  After this, all sound is somewhat muted and crackly until the power is cycled.

On my cabinet, the image is upside down.  I looked up the DIP switch settings and while there didn’t appear to be any way to change the default orientation, I flipped the Cabinet Type switch to “Cocktail”.  On a cocktail cabinet, the two players sit at opposite ends of the table, and the game flips the display depending on which player is currently playing.  With the board thinking it is in a cocktail cabinet, I can start a two player game and play only as the second player.  This is just how some games are, and if I ever put this on location, I’d have to remount the monitor.  For now, this is an acceptable workaround, though I really need to get a new 2P joystick!

–  Repair Log (1/16/2011):

I reviewed the board for issues, re-seating all the chips and cables before noticing a rather obvious defect:  a capacitor in the corner (near the Yamaha sound chips) is standing on one leg; only the positive lead is actually connected to the circuit board. I replaced it with a same spec cap from Radio Shack for $1.79.  The audio was now consistently loud with no clipping.  Satisfied that I wasn’t possibly causing damage to the board by throwing unregulated power around, I sat down and enjoyed a few rounds.  I made it to the third level and encountered no issues.    My first impressions of the game itself were not great, but after spending some time with it, I’ve come to like it.  Seems similar to Thunder Force II.

As you can see in the image above, the board is pretty filthy, so I spent a little time cleaning it.  Cleaning PCBs is tedious and stressful work, so I really just worked on and around the bottom PCB and any CPUs.  The game was already running fairly cool, but keeping the dust off certainly doesn’t hurt any.

– Repair Log (1/19/2011):

No progress, but I added some photos I took while working on the board the other day, and cleaned up some cruft from the post above.  I played through to the 8th (and final, I believe) level the other night, and left the board up and running for a few hours.  No video glitches, and no spontaneous resets (my high score was still present when I checked up on it later), but that nagging RAM error and occasional self-check reboot are still present.

I didn’t mention it before, but while I was re-seating the chips and connections, I noticed this wire mod on the solder side of the top PCB.  I’m pretty useless at figuring out what electronics are doing by just looking at them.  I assumed whoever put it there knew what they were doing, but of course, I couldn’t rule out that it would be the cause of the RAM error.

I asked about this on IRC today, and got a little guidance.  When I have some time later today, I’ll take some clearer pictures of the top and bottom sides of the board, marking the location of the wire mod’s solder points on the top side, and what chips are involved.  Maybe this will also be a quick, easy fix.